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DOHC 750 cams, a plea for help.

  • Thread starter Thread starter RockyPatel15
  • Start date Start date
R

RockyPatel15

Guest
I just got around to removing my valve cover to check clearances on my 1980 GS 750E, and found the following:

http://i1302.photobucket.com/albums/ag130/mikesdapperedpics/Mobile Uploads/image_zpsoina5dpy.jpg

http://i1302.photobucket.com/albums/ag130/mikesdapperedpics/Mobile Uploads/image_zpsm0q7uhsc.jpg

Now, I'm no expert, but after digging around here a bit I get the impression that those are toast. I could very well be mistaken. The surface feels entirely smooth, and there's no discernible groove that I can feel, but I'm not sure just how to determine whether they are salvageable or not. Anybody have a more informed prognosis?

In the likely event that I will need to replace that cam, should I just do both at the same time? Any other components I should replace while I'm in there? I'm also having a hell of a time finding cams for my particular bike (this is becoming a bit of a trend). Anybody have any sites I should check out in my hunt? They are backordered on partsoutlaw, which was my saving grace for the rather elusive brake caliper pistons for my bike.

If anybody is still actually reading this far, one more question for you. If this is going to turn into an extensive project, any other things I should check out while I've got the motor all apart? I have the clutch cover and stator cover off to replace the stator, gaskets, and fasteners all 'round. Is there anything else I should have a look at while I've got the various cases open and perhaps proactively replace? The bike has around 21k miles, but only about a thousand of them are mine. The PO didn't treat her very well.

Thanks all.
 
Cams and rockers. Shim the oil pressure relief spring. You are not the first with that problem.
 
Nessism said:
Cams and rockers. Shim the oil pressure relief spring. You are not the first with that problem.
Click to expand...

Does shimming the oil pressure relief spring mitigate the oil delivery problem these models have?
 
Oh look, someone sorta in my neighborhood. Replacement part costs add up quickly ( and can be hard to find) these plain bearing engines need oil. You say you put 1000 miles on this - any unpleasant noises noticeable from crankshaft ?

Put bike/model/year in your signature to aid others .this is 1980 gs750e?
 
You've got it, Tom. Just edited my signature, thanks for the tip.

The only noise I noticed seemed to be lifter noise, which I only noticed in about the last 500 miles. That's not to say it wasn't there, but getting the damn thing running reliably is still a work in progress.
 
I have a 1980 750 engine I can part out if you can't find the parts you need in the next few weeks. Haven't looked inside yet.
 
From what I could see, it looks fine. I have the same bike with 59,000 miles on it.
 
If they are perfectly smooth, they're probably fine. My 750 has similar discoloration and only 11,000 miles.

If you want to be sure, you can always remove them and put a micrometer on them, the service manual has the specs.
 
eil said:
If they are perfectly smooth, they're probably fine. My 750 has similar discoloration and only 11,000 miles.

If you want to be sure, you can always remove them and put a micrometer on them, the service manual has the specs.
Click to expand...

Excellent, that'll be my next step. I'd rather just adjust the valves and be done with it than spend many (more) hundreds of dollars.

@tkent02, if these truly are shot then I'll probably be looking you up. The cheapest replacement I've found, just for the cam alone, is $265. That's not even counting the rockers and such.
 
RockyPatel15 said:
I just got around to removing my valve cover to check clearances on my 1980 GS 750E, and found the following:

http://i1302.photobucket.com/albums/ag130/mikesdapperedpics/Mobile Uploads/image_zpsoina5dpy.jpg

http://i1302.photobucket.com/albums/ag130/mikesdapperedpics/Mobile Uploads/image_zpsm0q7uhsc.jpg

Now, I'm no expert, but after digging around here a bit I get the impression that those are toast. I could very well be mistaken. The surface feels entirely smooth, and there's no discernible groove that I can feel, but I'm not sure just how to determine whether they are salvageable or not. Anybody have a more informed prognosis?

In the likely event that I will need to replace that cam, should I just do both at the same time? Any other components I should replace while I'm in there? I'm also having a hell of a time finding cams for my particular bike (this is becoming a bit of a trend). Anybody have any sites I should check out in my hunt? They are backordered on partsoutlaw, which was my saving grace for the rather elusive brake caliper pistons for my bike.

If anybody is still actually reading this far, one more question for you. If this is going to turn into an extensive project, any other things I should check out while I've got the motor all apart? I have the clutch cover and stator cover off to replace the stator, gaskets, and fasteners all 'round. Is there anything else I should have a look at while I've got the various cases open and perhaps proactively replace? The bike has around 21k miles, but only about a thousand of them are mine. The PO didn't treat her very well.

Thanks all.
Click to expand...

The exhaust rocker arms on the early 16 valve 750s have a split pad. That's why you see the discolorization like that. As long as the cam lobes are smooth across & have no grooving the rockers are good. Just so you know, an 1100 motor bolts right in & is a LOT more fun AND reliable!!
Ray.
 
"...Just so you know, an 1100 motor bolts right in & is a LOT more fun AND reliable!!"

adjust valves and see how it runs. If any mechanical issues, consider ray's advice.
 
tom203 said:
"...Just so you know, an 1100 motor bolts right in & is a LOT more fun AND reliable!!"

adjust valves and see how it runs. If any mechanical issues, consider ray's advice.
Click to expand...

Yes, yes they are far more fun, and run SO much smoother. Mine didn't scare me anymore. That had to change... :emmersed:

Also had a valve tip issue due to the poor oiling. Considering what it would have cost to fix that, versus the cost of a running 1100...:rolleyes:
 
Last edited:
You guys are a bad influence. I'd been daydreaming of dropping in an 1100 motor if enough issues turned up with the current mill. Lead me not into temptation, I can find the way myself...

I'll be picking up a micrometer and checking if the cam lobes are in spec this weekend. In the meantime, I'll be praying to whatever deity pops into my head. I'm going to address the potential oiling issue, check out the pump, strainer, filter, etc either way, as well as shim the pressure relief spring. Thanks again for all the input, you guys are fantastic.
 
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